John,
I would not argue the percentage of distortion that you were measuring in transmitted sound through a compression driver and waveguide combination, but what percentage of this was actually because of the throat expansion rate loading and what was caused by poor design? Typically with the majority of compression drivers the actual transition from the diaphragm to the compression driver exit we have multiple sectional changes. Looking to the past the vast majority of compression drivers though roughly following an exponential expansion the actual sections at least in the final section of the throat are conic in section. Then we have the poorly conceived transitions from this conic section to the typical radial horns 90 degree or even 60 degree mouth sections attached to the first section of the waveguide. This transition was a fairly crude shape change to say the least and this area causes much in the way of reflective and defractive anomalies in this transitional area. So to blame the majority of the problem to the simple compressive nature of the expansion rate would seem to be an over simplification of the phenomena. Geedlee and I went down the same road way back in the thinking of this area of the waveguide and I would be interested in what he thinks about the causes of this so called throat distortion and what percentage is caused by what parts of the physical design and what percentage would be caused by the simple expansion rate from the diaphragm to the waveguide exit?

Esperado, it appears that you do not take horn throat distortion seriously

"...what percentage is caused by what parts of the physical design and what percentage would be caused by the simple expansion rate from the diaphragm to the waveguide exit?... "
And the horn resonances. i see nothing to add.

A i said, i'm not able to make a decision between a good driver/horn system assembly and the best cone, for normal levels, just looking at the distortion curve at different levels...
At low and medium levels, driver is way better, as level increase the curve increase with a faster slope. May-be this is what i like, this impression of improved dynamic ?

To be true, i'm not any more in concern with PA since 2 or 3 decades. When i was, our problems were not with HD, but with hall's acoustic, trucks and material problems, AC power problems, whether, time, money, roadies management, lack of sleep, hostels and food, human relationship with musicians and their managers etc...
I can just make a old fart ascertainment: Modern PA more miniaturized systems are not so good than were our gigantic walls. Less dynamic, less definition, rolling compressed sub basses... Less distortion ? May-be.

Christophe, I get it. I know exactly what you're after in sound, and what your system is able to achieve. I've only heard it a couple of times in other systems, one was a PA setup, interestingly enough, but the vast majority of so-called high end gear, no matter how expensive, is pretty hopeless at doing it.

The key is ensuring that certain types of distortion are maintained at a low enough level when running at realistic levels, and this is actually very difficult to achieve if one just assembles a system in the normal fashion. One can be lucky: high efficiency speakers combined with powerful amplifiers is the easiest way to get there, but inadequacies of engineering, every weakness in the components will scream at you; so, many just give up going this route and fall back to the cosy, nicey, nicey, conventional hifi sound.

Only the brave, or the foolish, choose to go the more difficult road ...

You, and Mr Curl are true on this: Designing the passive filter was a nightmare, asked years of tuning and kilometers of Buel &Kjaer's paper.
Both for him for his demonstration model, and for I, at home. It was a hard work to find a bass loudspeaker with the desired characteristic, good Thiele and Small parameters, able to go up to 700hz (1500 at home) without fractionating and flat enough. We both of us had to test several.

Even setting the level of the upper way (horn) 1/2 db too high or low, and your all system loose all its balance.

I'm listening to Mr Curl complaints about throat distortion, and, when my Friend François invited me to listen to his new wooden horn, designed with this new spheric waves calculation method, i was very skeptical, would never imagine myself using a horn in my home system.

The fact is that i have never listened to a system with so little subjective distortion, even at high level, so detailed, precise, transparent and balanced sound.
More than that, the enclosure character change in an incredible way from a record to an other.

I was never satisfied with mediums reproduced by cones. They fractionate, i can hear the color of the cone material, parasitic vibration of suspension, the sound turn both aggressive and "limited" with high levels and transients.

As i was never satisfied with separated tweeters: At those high frequencies, it seems impossible to filter them with "coherency". See what i mean ? You hear *trebles*, while you never hear trebles in real life.
Here, with a transition frequency at 700Hz, while the two transducers have the same surface, you do not notice any problem of transition and connection between the ways.

Oh, mr. Curl, did you had the idea, for PA, to try to compensate as much as possible the levels's non linearities of horns assemblies, introducing, before amps, an opposite expansion curve ? With DSPs, todays, it would be something possible.

The fact is that i have never listened to a system with so little subjective distortion, even at high level, so detailed, precise, transparent and balanced sound.
More than that, the enclosure character change in an incredible way from a record to an other.

A good description of the end goal ...

Quote:

I was never satisfied with mediums reproduced by cones. They fractionate, i can hear the color of the cone material, parasitic vibration of suspension, the sound turn both aggressive and "limited" with high levels and transients.

As i was never satisfied with separated tweeters: At those high frequencies, it seems impossible to filter them with "coherency". See what i mean ? You hear *trebles*, while you never hear trebles in real life.

But ... I have found that playing around with the speaker configuration is not the only way to achieve the result. There is another approach, which is to ensure that the electronics are working as cleanly, as competently as possible. If the circuits are working correctly, then the supposed limitations of the speakers are no longer an issue, they don't significantly, subjectively, degrade the sound.

Esperado, it is useless to talk about speaker design, if you do not know what I am talking about.
For the record, I use WATT's at home, for many years I had K-horns.

Please, master, forgive my miserable ignorance *

I don't know WATT, can-you provide a link ?
About Klipschorn's, this kind of "Donald Duck"s sound we were talking about ?

*During the early 70s, I was in charge of the electo-acoustic Research and developpment office of the first French hifi manufacturer at the age of 25, spending my life in the LNE's big anechroic chamber. We provided pro enclosures for BBC, working with KEF, Mr Leon (Elipson), Gérard Gogny (Orthophase), Audax laboratories etc... (learning from all those inventors and passionated guys)...